Spindle Model Responsive to Mixed Fusimotor Inputs and Testable Predictions of β Feedback Effects

Maltenfort, Mitchell; Burke, Robert E.

doi:10.1152/jn.00942.2002

Cited by 28 publications

(40 citation statements)

References 58 publications

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“…Experimental data strongly suggest that both ␥-and ␤-MNs are excited by spindle afferents Rymer 1985, 1987). Predictions of spindle models agree with the empirical findings (Maltenfort and Burke 2003; see for review Prochazka and Gorassini 1998). It is unlikely, however, that the increase in Ia firing reported here might activate ␥-MNs.…”

Section: Discussionsupporting

confidence: 86%

“…Second, ␥-MNs and Ia fibers were initially excited, but ␣-MNs were inhibited as indicated by EMG depression, which also excludes excitation of skeletofusiomotor or ␤-MNs. (Maltenfort and Burke 2003; see also Appelberg et al 1983a;Wuerker and Henneman 1963). Third, afferent fibers that are originated in the pudendal skin and in the external genitalia induce firing of ␥-MNs to hind limb muscles.…”

Section: Discussionmentioning

confidence: 96%

“…Appelberg et al (1983a) reported that group I afferents produce little effect in a small proportion of homonymous ␥-MNs, but group II afferents produces autogenetic excitation in ϳ40% of these MNs (Appelberg et al 1983b). In addition, it cannot be excluded that the sustained Ia firing might activate ␤-MNs Rymer 1985, 1987;Maltenfort and Burke 2003). It would be interesting to test whether the stimulation of SPN produces sustained firing of group II afferents and ␤-MNs.…”

Section: Discussionmentioning

confidence: 99%

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Gamma→Alpha Linkage and Persistent Firing of Ia Fibers by Pudendal Nerve Stimulation in the Decerebrate Cat

Raya

Ramirez²,

Muñoz-Martínez³

2004

Journal of Neurophysiology

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. The sensory pudendal nerve (SPN) was stimulated in decerebrate female cats. Spikes of single Ia muscle spindle afferents from the medial gastrocnemius (MG) muscle were recorded in dorsal root filaments. Electroneurography (ENG) was recorded in a cut nerve filament to the MG muscle; MG electromyography (EMG) was also recorded. Single shock to SPN induced discharges of small ENG spikes (SS) with similar amplitude to that of gamma spikes elicited by ventral root stimulation. Thus SS were identified as gamma spikes. The latency of the gamma discharge was ϳ15 ms. As expected, the onset of the gamma discharge preceded a discharge of Ia spikes; the time difference between both discharges was ϳ5 ms. After the initial bursts, the Ia and the gamma activities paused during 20 -30 ms but later increased again to last ϳ1 s. After the shock, the EMG activity was depressed during ϳ50 ms; later, motor-unit spikes may show transient activation. Thus the onset of the gamma activation preceded the activation of motor units (gamma3alpha link). Trains of shocks (1 or 100 Hz) to SPN induced a sustained increase in the frequency of gamma spikes, Ia spikes, and motor units that outlasted the train by 20 -120 s. The sustained firing of Ia fibers might trigger or help to trigger and maintain the response of alpha-motoneurons.

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

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Gamma→Alpha Linkage and Persistent Firing of Ia Fibers by Pudendal Nerve Stimulation in the Decerebrate Cat

Raya

Ramirez²,

Muñoz-Martínez³

2004

Journal of Neurophysiology

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“…Several models of spindle afferent activity have been developed to account for the growing base of physiological data (Chen and Poppele 1978;Crowe 1968Crowe , 1970Hasan 1983;Houk et al 1981;Lin and Crago 2002;Maltenfort and Burke 2003;Matthews and Stein 1969;Rudjord 1970;Schaafsma et al 1991). Prochazka and Gorassini (1998) compared the performance of some of these models to experimentally recorded primary and secondary afferent activity from cat hamstring muscles during locomotion.…”

Section: Comparison With Previous Modeling Attemptsmentioning

confidence: 99%

“…Throughout the years, several attempts have been made to formalize these assumptions in mathematical models capable of accurately capturing spindle activity over the wide range of kinematic and fusimotor conditions in which spindles naturally operate. These modeling approaches involved either transfer functions (Chen and Poppele 1978;Matthews and Stein 1969), nonlinear functions based on curve-fitting (Houk et al 1981;Maltenfort and Burke 2003), or reduction to constituent anatomical components (Hasan 1983;Lin and Crago 2002;Rudjord 1970;Schaafsma et al 1991). As a consequence of the complex nature of spindle responses, the earliest models attempted to model primarily afferent activity in the absence of fusimotor activation, with the exception of Hasan (1983).…”

mentioning

confidence: 99%

Mathematical Models of Proprioceptors. I. Control and Transduction in the Muscle Spindle

Mileusnic¹,

Brown²,

Lan³

et al. 2006

Journal of Neurophysiology

186

181

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. We constructed a physiologically realistic model of a lower-limb, mammalian muscle spindle composed of mathematical elements closely related to the anatomical components found in the biological spindle. The spindle model incorporates three nonlinear intrafusal fiber models (bag 1 , bag 2 , and chain) that contribute variously to action potential generation of primary and secondary afferents. A single set of model parameters was optimized on a number of data sets collected from feline soleus muscle, accounting accurately for afferent activity during a variety of ramp, triangular, and sinusoidal stretches. We also incorporated the different temporal properties of fusimotor activation as observed in the twitchlike chain fibers versus the toniclike bag fibers. The model captures the spindle's behavior both in the absence of fusimotor stimulation and during activation of static or dynamic fusimotor efferents. In the case of simultaneous static and dynamic fusimotor efferent stimulation, we demonstrated the importance of including the experimentally observed effect of partial occlusion. The model was validated against data that originated from the cat's medial gastrocnemius muscle and were different from the data used for the parameter determination purposes. The validation record included recently published experiments in which fusimotor efferent and spindle afferent activities were recorded simultaneously during decerebrate locomotion in the cat. This model will be useful in understanding the role of the muscle spindle and its fusimotor control during both natural and pathological motor behavior. I N T R O D U C T I O NThe muscle spindle is a sense organ found in most vertebrate skeletal muscles. In a typical mammalian lower limb muscle, several tens (or even hundreds) of muscle spindles can be found lying in parallel with extrafusal fibers and experiencing length changes representative of muscle length changes (Barker 1962;Eldred et al. 1962). The spindle has been found to play a dominant role both in kinesthesia and in reflexive adjustments to perturbations (Hulliger 1984;Matthews 1981). Its sensory transducers (primary and secondary afferents) provide the CNS with information about the length and velocity of the muscle in which the spindle is embedded. The spindle provides the main source of proprioceptive feedback for spinal sensorimotor regulation and servocontrol. At the same time that the spindle supplies the CNS with afferent information, it also receives continuous control through specialized fusimotor efferents (static and dynamic fusimotor efferents) whose task is to shift the spindle's relative sensitivities over the wide range of lengths and velocities that occur in various natural tasks (Banks 1994;Matthews 1962).The spindle consists of three types of intrafusal muscle fibers: long nuclear bag 1 and bag 2 fibers and shorter chain fibers ( Fig. 1A) (Boyd et al. 1977). Typically, one bag 1 , one bag 2 , and about four to 11 chain fibers lie in parallel within a spindle (Boyd and Smith 1984). The bag 1 ...

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Control of Mammalian Locomotion by Somatosensory Feedback

Frigon

Akay

Prilutsky

2021

Comprehensive Physiology

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When animals walk overground, mechanical stimuli activate various receptors located in muscles, joints, and skin. Afferents from these mechanoreceptors project to neuronal networks controlling locomotion in the spinal cord and brain. The dynamic interactions between the control systems at different levels of the neuraxis ensure that locomotion adjusts to its environment and meets task demands. In this article, we describe and discuss the essential contribution of somatosensory feedback to locomotion. We start with a discussion of how biomechanical properties of the body affect somatosensory feedback. We follow with the different types of mechanoreceptors and somatosensory afferents and their activity during locomotion. We then describe central projections to locomotor networks and the modulation of somatosensory feedback during locomotion and its mechanisms. We then discuss experimental approaches and animal models used to investigate the control of locomotion by somatosensory feedback before providing an overview of the different functional roles of somatosensory feedback for locomotion. Lastly, we briefly describe the role of somatosensory feedback in the recovery of locomotion after neurological injury. We highlight the fact that somatosensory feedback is an essential component of a highly integrated system for locomotor control.

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Spindle Model Responsive to Mixed Fusimotor Inputs and Testable Predictions of β Feedback Effects

Cited by 28 publications

References 58 publications

Gamma→Alpha Linkage and Persistent Firing of Ia Fibers by Pudendal Nerve Stimulation in the Decerebrate Cat

Gamma→Alpha Linkage and Persistent Firing of Ia Fibers by Pudendal Nerve Stimulation in the Decerebrate Cat

Mathematical Models of Proprioceptors. I. Control and Transduction in the Muscle Spindle

Control of Mammalian Locomotion by Somatosensory Feedback

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